The use of the telephone network for connection to data networks is currently growing at an exponential rate. More and more service providers are providing connections to, for example, the Internet at higher and higher bandwidths (data transfer speeds) for more and more users. Increasingly, more people are accessing such services at data speeds approaching or exceeding the bandwidth of normal telephone lines. The current state of the art computer data connector is a 28.8 Kbits per second (Kbps) modem, with 33.6 Kbps modems becoming available. However, for some applications, these modems still do not have enough bandwidth for large data transfers and, therefore, cannot handle the bandwidth required by some of the Internet, especially graphic or audio (or both) web pages. Furthermore, local switching systems are becoming overloaded because such large data transfers require that connections are held longer (in some cases, far longer) than normal voice calls, for which the systems were engineered.
A high bandwidth trunk (T1) connection to a home or small business is still relatively expensive (prohibitively so in most cases). As an alternative, many people are using an integrated services digital network (ISDN) telephone line for data communication, including connection to the Internet, at a higher speed than is obtainable through a voiceband modem. ISDN provides two "voice" and one "data" channel, otherwise known as 2B+D. The B channels operate at 64 Kbps, and the D channel operates at 16 Kbps. The B channels are intended for voice or data and the D channel is generally intended for signaling (i.e., setting up calls, etc.). By using an ISDN connection, a user may obtain data transfer speeds of up to 128 Kbps (using both B channels) for the cost of a single ISDN line. As more and more people are opting for ISDN (especially as more people begin to work at home), the cost of ISDN is dropping. Therefore, it is highly likely that in the near future there will be many ISDN connections, many of which will be accessing data networks (including the Internet) at some point or another.
Turning to FIG. 1, an illustration of the current art connection of an ISDN modem to a data network is shown. In this system, a personal computer or work station 12 of some variety known in the art is connected to an ISDN "modem" 14. There are many such ISDN modems available in the market place. ("ISDN modem" is a misnomer, since there is no modulation or demodulation. "Translator" would be a better term, but "modem" is used in the art, thus will be used herein). Alternatively, ISDN modem 14 may be an analog telephone/PC interface as described in U.S. Pat. No. 5,305,312, which issued Apr. 19, 1994 to M. Fomek, et al., and assigned to the assignee of the current invention (the specification of which is incorporated herein by reference). In this manner, a personal computer, work station or other computer-type system may be connected via ISDN to the public switched telephone network (PSTN) at data speeds of up to 128 Kbps.
ISDN line 16 is connected to local digital switching systems 20, as is known in the art. Such switching systems may be the same or similar to Lucent Technologies' 5ESS.RTM. ISDN switch as described in U.S. Pat. No. 4,592,048, which issued to M. W. Beckner, et al., on May 27 1986, and is also assigned to the assignee of this current invention (for a further discussion of the components of an ISDN switch, please refer to the previously referenced Fornek patent).
Local digital switch 20 delivers receives/transmits data between ISDN line 16 and transmission facilities, such as DS 3 lines 22 to/from a toll switch 24. Toll switch 24 may be the same or similar as AT&T's 4ESS.TM. switch, which is described in the Bell System Technical Journal (BSTJ), Vol. 56, No. 7, pgs. 1015-1320, September, 1977, which is incorporated herein by reference. Toll switch 24 includes central control 26 and interfaces 28 to transmission facilities 22, comprising a DS 3 to DS 0 interface, as is known in the art. Switching fabric 30 of toll switch 24 comprises a plurality of timeslot interchange units (TSI) represented by TSIs 32 and one or more time multiplex switches, represented by TMS 34. Time multiplex switches 34 are known in the art and described in the above BSTJ reference. Long distance switch 24 switches the data call through DS 3 interfaces 28, TSIs 32, and TMS 34 to another transmission facility 38 and to a data network server 40.
Data network server 40 comprises a multiplicity of units in order to connect a data stream from the telephone network to the Internet. Data network service center 40 may be in the same premises as long distance switch 24 or may be in a remote location. Data network service center 42 comprises a DS 3 demultiplexer 42, which demultiplexes DS 3 into 28 DS 1s comprising 672 DS 0 channels. Each channel is delivered to and received from a channel banks 44, as is known in the art, which translates between pulse code modulated (PCM) as is used in the telephone art and ISDN data. ISDN data lines are connected between channel bank 44 and a plurality of ISDN modems (represented by ISDN modems 48) in ISDN modem bank 50. ISDN modems 48 translate to the data protocol from ISDN into a local area network protocol such as Ethernet and transmit a data on local area network 52 to a broadband router (B-router) 54. B-router 54 connects the ISDN channels to the Internet or other data network 56.
In the system of FIG. 1, there are many network facilities being used. For example, a complete connection through long distance switch 24 is made for every ISDN connection. DS3 facilities are used to connect between long distance switch 24 to data network service 40, requiring electrical and/or optical transmission facilities. Most importantly, there is a one-to-one ratio between ISDN modems at the telephone network/data network interface, which, in a heavily used system, is exceedingly expensive.
Therefore, a problem in the art is that there is no economical system for connecting ISDN-based data links to data networks, such as the Internet.